Tunnels 04, Closer

have to wait long to find out what it was. He was right. "There's no question that the skull from the stake is human. Homo sapiens , same as you and me," Dr. Burrows announced. "And so is this other one, from the pair in the compartment."
    "It's a darker color," Will observed.
    "That's not important -- focus on the smaller skull next to it, which the Ancients thought was significant enough to preserve in the pyramid. Tell me what you see," Dr. Burrows instructed Will, snatching up the skull and pushing it into his son's hands.
    "It's heavy. It's definitely a fossil," Will observed, gauging its weight. "And it looks different from a human sk--"
    "I'll say it does," Dr. Burrows cut in. "What about the overhanging brow, and the way the jaw protrudes much more than the others?"
    "It isn't human?" Will asked.
    "I only took a couple of courses in anthropology so I'm no expert. However, to my eye, it has features that are neither human, nor fully simian," Dr. Burrows gushed.
    "Simian?" Will said. "So it's not an ape or a monkey either?"
    "No, not in my opinion, because--" Dr. Burrows interrupted himself, waving his hands enthusiastically. "Remember back in Highfield when you were young -- I told you all about the missing links and Leakey Man?"
    "Bedtime stories about Leakey Man," Will recalled, allowing himself a chuckle. "Yes, I remember... the skull that was dug up in a river in Africa."
    "Precisely! It was solid proof of one of man's distant ancestors. But while skulls from the Homo erectus stage and a number of other stages that came before it have been discovered, there's absolutely nothing to demonstrate the transitional steps from ape to man. Nothing at all. No fossil remains have been found yet for the so-called hominid gap, which was millions of years long. Don't you think that's odd?"
    "Yeah -- very," Will answered.
    "Of course it is. There's always been this unexplained mystery as to why there's a gaping hole in the human evolutionary record."
    "And?" Will urged his father.
    Dr. Burrows snatched the small skull from his son and replaced it on the table. "This may sound a bit off the wall... but what if they've never been found on the surface because..." He now stuck his finger in the air, urging Will to finish his assertion.
    When Will didn't answer quickly enough, Dr. Burrows continued impatiently. "Because it all went on down here."
    "Ah," Will put in, but his father was in full flow now.
    "What if this inner world was the melting pot of human evolution, and possibly even the evolution of an ark-full of other animal species?" Dr. Burrows threw his arms open at the jungle around them. "I mean, all the plants and trees we can see before us are specially adapted to live without night -- all the flora on the surface need darkness for photosynthesis and to trigger photoperiodic changes."
    "Photo -- what? " Will asked.
    Dr. Burrows ignored his question, talking rapidly. "So my theory is the 24/7 sunlight in this closed ecosystem actually promotes accelerated evolution. And it also promoted our accelerated evolution."
    "You're saying apes evolved into humans here in this inner world, and then somehow got back to the surface," Will said.
    "Precisely!" Dr. Burrows exclaimed again. "Which is amazing... and the Ancients, the people who lived here, were clued-up enough to be interested in it, too. From what's written on their pyramid, they were close to figuring it out." He took a breath. "And what this also means is that I've probably just made the single most important discovery of the century."
    "Another one?" Will murmured under his breath, shaking his head at the old skulls.

    * * * * *

    Drake glanced at his watch as he squatted by the launch on the quayside. "Sun up is around six hundred hours," he said. Although he could have used his headset to search the former airfield up above for any tracks Chester might have left there, he and Eddie had decided it would be better to wait until dawn. To pass the time, Drake was making an inventory of the rations in the holdalls. Buried under the packets, he found something that he took out very slowly.
    It resembled a rather crude gun.
    "Weapon?" Eddie asked, immediately interested.
    Drake shook his head. "No, it's a prototype low-frequency detector. It hasn't been properly trialed yet, but if we got the spec right, it should work as a tracking system -- even over great distances underground."
    Eddie was intrigued. "Through the Earth's crust?" he said.
    Drake was examining the